Furnace



Sept. 29, 1931. w GRQTHE 1,825,059

FURNACE Filed July 9, 1928 5 Sheets-Sheet 1 FIE :L

INVENTOR Wo/fer Grof/ze A TTORNE YS Sept. 29, 1931. w, GROTHE 1,825,059

' FURNACE Filed July 9, 1928 5 Sheets-Sheet 3 IN VEN TOR A TTORNE YS Sept. 29, 1931. w. GROTHE FURNACE Filed July 9, 1928 5 Sheets-Sheet 4 IF I E 4= Hui] 7 I '5 4 6 7e Z; 7/ V 6/ a;

IN VEN TOR W. G ROTH E se tfzs, 1931.

FURNACE Filed July 9, 1928 5 Sheets-Sheet 5 Hll INVENTOR Wa/fzr Graff/z.

Patented Sept. 29, 1931 UNITED STATES A EN QFFWE WALTER GROTHE, OF SAN LnAnnRo, canrronma, Assrsrion Fro oATERr'I L n' TRACTOR 00., or'sAiv LEANDRO, ent re-am, Aconponnrron orcALIromnA i rurmncn My invention relates to furnacesprimarily intended for use in. heat treating material and particularly. relates toa furnace of this type which is heated by electricity. An object of my invention is to provide a furnace which is wellinsulated to conserve heat, with the insulating material occupying provide means for supporting'a portion of the interior structure from furnace.

the top of the Anadditional object of the invention is to provide, in a furnace having a power rotated hearth, a manual rotating means taking precedence over the. power rotating means. I

A still further object of the invention, is

" to dispense with the usual fjrameWork of ing elements. V

My inventlon possesses other advantageous features, some of which w1ththe forerefractory material for supporting. the heatgoing will be set forth at length in the following description where I shall outline in full that form of the furnace of my invention,,which Ihave selected for illustration in the drawings accompanying and forming 535 part of the present specification. In said drawings I have shown one form of furnace embodying my invention, but it is to be understood that I do not limit myself to such form sincethe invention, as set forth in the claims, maybe embodiedin aplurality of forms. N I i In the drawings! I I c Fig. 1 is a plan of the furnace of my invention with the cover removed to disclose some of the bracing.

Fig. 2 is a vertical section of my furnace, the plane of section being indicated byline 2-2 ofFigrl. r x r Fig. 3 is asection on'a plurality of planes,

quickly cooled I Preferably I Application -fi1ed J'uly 9, 1928. Serial No. 291,322.

these planes being indicated by lines-3 o igr v Fig. 4 is a side elevation showing in detail 7 aportion of therotating mechanism for my furnace. p ig. 5 discloses the door actuating mech- Fig. (ishows thecentral shaft, with some of its associated parts in section.

In its preferred form, the furnace of my invention comprises a shell within which is ,aerevolving hearth arrangedto be moved .into and out of. operative position, and also usually includes an inner" wall suspended so as not-to interfere with thehearth.

In the embodiment illustrated in the accompanying drawings, the furnace c0 m i-prises an outer shell 6 reinforced bya channel 7 at its lower circumference and resting upon; a suitable base ,8. The shell 6 is con .veniently a metal cylinder stiffened at its "upper end by a channel 9 and closed by a cover. 11, Within the. shell .6 I preferably .provide an outer wall 12usually comprised of refractory insulation 13 conveniently held in place and backed by a suitable heat- .insulating substance 14. The outer; Wall is generally arranged in a cylindrical form and is largely supported in the upper portion-of the .shell-(i by brackets 16. and 17 properlyg secured in; place. Inasmuch as the refractory; insulation does not extend for the full height of the shell, there is provided an upper, thermally insulated zone in which the furnace heat is well retained and 35 lower, uninsulated zone-in which radiation and dissipation of beat are relatively rapid,

concentric with the outer cylindrical wall 12, I; provide an inner wall'l 8 likewise of refractory insulation 19 and suitable heat insulating materiaLZl. The inner wall is generally. of cylindrical form and .preferably is supported from -above.t-The support a plate 24 having a collar 27 into lwhichzis threaded a centrally depending, '100 l revolving hearth to carry the parts to be I hollow column '26.

wall 18 and the outer wall 12 is bridged over by suitably arched insulating refractory members 32 usually interlocked with the members 13 and 19 and covered with the insulating material 21. J g

lVithin the furnace I preferably provide a treated. This hearth 33 generally includes suitably arranged refractories disposed on an annular table 34 comprised of a-pair of annular castings. The table at its inner and outer peripheries is formed'with troughs 36 carrying sand 37 or other suitable sealing material into which project an annular ring 38 depending from the bracket 17 and an annular ring 39 depending from the platform 29. In this manner there is provided a seal against heat loss and at the-same time relative rotation and some axial trans lation is'p'ermittedbetween the hearth 33 and the stationary inner and outer linings "1S and 12.

""The table 34- is mounted on a spider L1 whichcarriesat its hub 4&2 a threaded'sleeve 43 in engagement with the threaded portion 44 of a central shaft46. The shaft 46 extends vertically throughout the shell 6 and at'its lower end rests on a thrust bearing 47 suitably located within and protected; by a casing 4:8 supported onthe base 8 and positionedv by' stay rods 49 extending radially to the lower periphery of the shell 6. Shaft 46 isfurther provided with bearings 51' and 52located at opposite ends of the hollow'column'26 and designed to carry radial loads.

Ordinarily, it is intended that the spider 451 and the shaft 46 rotate as a unit and for this reason a two piece lock-nut 53 engages the threaded portion 14 and holds the hub 4.2

firmly in engagement with washers 5tbearing on a shoulder in the shaft46. Inasmuch 'as the spider 11 normally does not travel axially along the shaft 46, I' provide a cover for the unused threaded portion in order to protect it from dirt. This cover may be a shield made intwo' pieces'56 and 57 united ateither end by bolts 58 passing through 'split collars 59.

Means are provided forimparting aslow rotation to the central shaft 46 in order to fre'volve the hearth'33. This mechanism is particularly shown in Figs. 1, 2 and 4, which disclose a pair of cross members 61and 62 spanning the beams 22 and 23. Suspended between the beams is an electric motor63 which drives a reduction gear 64 supported a yoke 81 secured to the plate 24. exerts a sufiic'ient retardantforce to' preclude rotary movement of the hearth 33 exbetween the members 61 and 62. Projecting upwardly from the reduction gear is a crank pin 66 carrying a rectangular block 67 slidable between the parallel tines of a fork 68 forming one end of a bell crank 69 pivoted at 70 to a lever which in turn is freely rotatable on the central shaft 46. The other arm 72 of the bell crank is adjustably connected through a spring 73 to the-lever 71., A stop 7 ljconstrains relative movement of the bell crank 69 and the lever 71in one direction. The rotary movement of the electric motor 63 is transmitted through the reduction gearing 64 and revolves the pin 66. This movement is effective to reciprocate the block 67 within the fork 68 and imparts an oscillating movement to the lever 71. If for any reason the lever 71 cannot'follow the movement of the bell crank 69 there is relative motion about the pivotalpoint 70 the mechanism is thus prevented from transmitting excessive loads. The oscillating movement of arm71 is translated into rotary movement of the shaft 46. A' pawl 75 is pivoted to the 'arm'71 and engages a ratchet 76 formed on the periphery of a disc attached securely to the shaft 46. In order to constrain reverse movement of the central shaft and its attached hearth 33, a brakedrum 77 is secured to the upper end of a shaft 16 and is encompassed by a pair of bands 78 which are pressed together by a spring 79 and are adjustably anchored in cept under the superior urging of the ratchet device. The described mechanism is effective to rotate the hearth continuously at any' selected speed while the rate of rotation can easily be varied by changing the ratio of the reduction gear 64: and by altering the location of the crank pin 66 with respect to its rotational axis.

Preferably, I also provide a supplementary, manually operated means for rotating the hearth through the intermediary of the shaft 46 and this usually comprises a yoke 83 freelyournaled on the central shaft 16 and alongside the shell 6. By manually rotating the hearth it is possible, Without in any way interfering with the power drive, to examine any portion of the material being treated and to restore the hearth to its original positlOn.

Access to the interior annular chamber 31 'within which are placed the articles to be treated, is afforded through a sliding door. This door preferably comprises a block 91,

made: up :of 'suitable insulating material,

The brake the door is adjustably limited by an auxiliary rod 97 carrying adjusting. nuts 98. The rod passes through an aperture in a portion of a frame 99 secured to the shell.

In order to counterbalance the weight of the block 91 and its operating mechanism, cables 101 are preferably secured to the cross member 94, pass over pulleys 102 journaled in the shell 6 and carry counterweights 103 at their opposite ends. The cross member 94 is vertically translated by a lever 104 I joined to it by links 106 and rotatable with a shaft 107 suitably journaled on the shell 6. The end of the shaft 107 carries a handle 108 conveniently disposed for actuation by the operator; Preferably the relationship and adjustment of the actuating linkages for the door 91 are such that the top of the door when lowered is exactly flush with the floor ofthe opening 92, as indicated by the dotted lines 109, in Fig. 2. Thus there is formed a continuous and smooth passageway for the materials being inserted into or withdrawn from the furnace. Further, by arranging the door 91 to rise from below,

the door where large heat losses would otherwise occur.

The heatis supplied to the furnace preferably by electricity and emanates from resistance ribbon 113 suitably suspended around the interior of the furnace on pins 11% directly embedded in the insulation thus dispensing with'auxiliary support. Leads for the resistance element 113 and for py rometers or other instruments are preferably carried to the interior of the furnace through passages 115 insuitable blocks 116 of refractory insulating material held in place by metal straps 117 secured to the shell and having bolts 118 which clamp the blocks.

116 in place. 7 g

In the usual operation of my furnace the parts have the relative positions shown in Fig. 2. lVhen electric current is passed through the resistance material 113, the entire chamber 31 is heated with. very slight thermal loss due to the effective insulation in the upper zone of the furnace. Pieces of material for treatment are inserted past the momentarily lowered door 91 onto the hearth 33 which is revolved during the normal operation of the furnace'by the mechanism driven by the electric motor 63. When the pieces have made substantially a complete revolution, they are withdrawn from the furnace through the opening 92 and generally are replaced by untreated pieces.

Occasionally a furnace ofthis type becomes: jarmrre'a dr for other i reasons it 'be comes necessary toga1n= access to the mte 'rior, for instance to'renew thesand seals or to clean out scale deposited byfthe work. "In ordinary furnaces it requires a period" of time usually measured in} days to; cool the furnace sufliciently to allow workon' the interior -thereof.- -"YVith my' construction it is *possible' to get atthe interior within time measured'inhours or'fminute's. Since the thermal Insulation of the j furnace is very complete and eifectiv heat is largely con- 1 fined to the upper zone, and an operatorca'n readilyenterithe-lower portion ofthe shell 46through suitable man holes121. '-When the shields 56 a-nd 57 and the" lock collar 53 are removed, v the shaft 46 and thespider 41 can be relatively rotated to lower the hearth 33 into the thermallyuninsulated lower zone of the shell 6. Usually' when-the bottom lining 33 is thus lowered whatever difficulty has arisen can be. rectified by suitable tools used through-the manholes-1121 but'in any case the entire furnace cools quickly largely .due .to the' rapi'd radiation of hea-t through theuninsulated lower shell 6 and to aircur- :rents which can be established throughthe man holes 121andalso through the opened :door91. x 1w It will be appreciated thatI'havepro- ".vided a. furnace which normally is very-*- efit is possible to utilize full insulation above :fectively sealed 'and insulated against the 'loss of heat I and :which thereforeoperates quite economically. ""lhefurna ce, however,

--iscapableiofrbeing adjusted so that itwill cool off very quickly .and .iaccess to the inteirior can be had-with dispatch; 'turesyare largely due to thexfact that the These feainsulation. and hearth are disposed and supp rted sucha way that. the 5 shell is divided int0.a:thermally insulated zone and a thermally. u-nins ulatedl zone and because the jhearth can be raised.

and lowered with celerity.

,- 1 Iclaimzllw; 1. a v :1. A furnace comprising a shell, a screw shaft in said shell, means for rotatin'g'said 1SC1'6W sha ft,a hearth'mountedzon said screw shaft fQP'tI'LllSliLtlOll upon relative rotation therebetween, and means for preventingrelable screw shaft within said shell, a rotatable hearth threadedly engaging said screw .shaft to translate said hearth, with respect to said shell upon relative rotation between said screw shaft and said hearth, and means" in a predetermined quantity and in only one for rotating said screw shaft and said hearth in unison with respect to said shell. 7

4. In a furnace employing a rotating hearth, a driving mechanism for rotating the hearth at a substantially constant speed, and manual means superior to the driving means for moving the hearth; I

5. In a furnace employing agrotatable hearth, a driving mechanism therefor including a power source and a ratchet mech-' anism' for transmitting power to-the hearth direction.

6. In a furnace employing a rotatable hearth, a driving mechanism therefor comprising a power source, a ratchet mechanism including a lever for rotating the hearth, and a connection between the lever and the driving mechanism'for transmitting only an approximately predetermined quantity of power to the hearth.

7 A furnace comprising an outer shell, an

outer wall in the upper portion of said shell, an inner wall suspended in the upper portion of said shell, a hearth supported on and rotatable with respect to a screw for. raising said hearth into operative relationship p with said inner and said outer walls, and

means for rotating said hearth and said screw as a unit.

8. A furnace comprising a circular outer shell; an outer wall-in the upper portion of said shell; an inner wall in the upper portion of said shell, said Walls being separated by an annular space; means for supporting said inner wall fromthe upper part of'said shell; a central shaft in said shell;

a spider threaded on said shaft and adapted to be raised and lowered thereon; means for rotating said spider and said shaft as a unit;

and a hearth resting on said spider.

9. In a furnace, a hearth and a shaft rotat-able to raise, lower, and rotate said 2 hearth.

10. In a furnace, a hearth, anda hearth.

In testimony whereof, I have hereunto set my hand. a WALTER GROTHE.

screw to ad ustably support and to rotate said 

